The Type IX U-boat was designed in 1935 and 1936 as a large ocean-going submarine for sustained operations far from the home support facilities.
It was derived from the Type IA[?], and appeared in various sub-types.

Type IXs had six torpedo tubes, four at the bow and two at the stern.
They carried six reloads internally and had five external torpedo containers (three at the stern and two at the bow) which stored ten additional torpedoes. The total of 22 torpedoes allowed U-boat commanders to follow a convoy and strike night after night.
As mine-layers they could carry 44 TMA[?] or 66 TMB mines[?], but many of the IXC boats were not fitted for mine operations.

Secondary armament was provided by one large Utof 105/45 gun with about 110 rounds. Antiaircraft armament differed throughout the war.
They had two periscopes in the tower.
Types IXA and IXB had an additional periscope in the control room, which was deleted in Type IXC and afterward.

Type IXB was an improved with an increased range.
It was the most successful overall with each boat averaging a total of over 100,000 tons sunk.

Famous IXB boats included U-123 under the command of Hardegen, which opened up the attack in the US waters in early 1942 known as Operation Drumbeat, and U-107[?] out of Freetown, Africa[?] under the command of Hessler, which had the most successful single mission of the war over with close to 100,000 tons sunk.